Ventilated ATEX container for process analyser (gas chromatograph)

For a customer in the Far East, ELECTROMACH has developed an explosion protected container for a process analyser for usage on an oil refinery.

Gas chromatograph

The gas chromatograph will measure the amount of hydrogen. This should be done at the refinery and as close to the process gas pipe as possible. For the most accurate result, the hydrogen measurement must be completed in a limited time frame. The length of the heated sample-pipe has a major influence on the amount of total time necessary for this measurement.

The Ex-container

The gas chromatograph will be installed in an explosion protected container. The container has been designed as a fully welded construction and has been insulated and specially coated to meet the extreme site conditions.

To guarantee the functioning of the analyser, the temperature inside the container will be kept on a average of approx. 25°C, while the temperature outside the container can vary between -5°C and +60°C.

The container will be equipped with an ATEX Ventilation & Air ConditioningSystem supplemented by an ATEX heater to ensure this temperature so that the system can function properly and can also be started at all circumstances.

The inside of the container has been classified as an ATEX Zone 2, IIB+H2 T3 area. Around the gas chromatograph a potentially hazardous area may occur, as the gas chromatograph measures the hydrogen content and works with pure hydrogen as a reference gas.

An ATEX Ventilation systems creates an under pressure in the container and thereby preventing the emergence of an explosive atmosphere. The system monitors and dilutes any hydrogen gas present with clean air, by creating a differential pressure between the inside and outside using ventilation. The amount of hydrogen in the atmosphere will be kept beneath the dangerous LEL level (Lower Explosion Limit) and will be monitored with H2 meters.

In consultation with the customer, the amount of oxygen will also be monitored, to ensure a safe working environment for the process operators who will be visiting the container on a daily base.

The ventilation system automatically adjusts the air inlet when a dangerous concentration of hydrogen or nitrogen will be measured. The signalling and communication of the gas chromatograph as well as the safety system are managed by the DCS system.

In this project Electromach was responsible for the engineering and production of the complete container assembly, containing the ATEX HVAC and ventilation unit, installation of the gas chromatograph and the associated process sample conditioning units outside the container and the Exde control panes.